Vehicles may use low frequency (LF) polling to detect the approach of a customer with a key fob provided for passive entry to the vehicle based on a recognized response from the key fob. However, other vehicles may park relatively close to polling vehicle and may also implement similar technologies. The LF signals transmitted from each vehicle may collide with the signals of another. That is, signals may overlap, causing the low frequency challenges to become corrupt and possibly unrecognizable by the key fob's receiver.
In an effort to avoid these corruptions and collisions, some systems use relatively short challenges at a higher polling rate. However, these signals may be difficult for the key fob's receiver to detect. Other systems may use longer challenges so that in the event of collision, some portion of the signal may survive and be recognizable by the key fob. However, these systems may occupy large amounts of ‘air space’ and be relatively unpredictable as to the collision probabilities. Additionally, longer LF challenges from the vehicle consume significantly greater current which may degrade the vehicle battery state of charge required for cranking. As such, there is a need for a proximal scanning system that actively avoids collision from other low frequency signals.